your modem config file with the set downstream frequency would be used more so if you had two bonding groups.
example, 8 channel bonding, a bunch of video channels and then another group of 8 channel bonding. if you wanted a modem to use the 1st group of 8 channels, you would configure the modem file for a frequency on the 1st group. if you wanted the modem on the 2nd or higher group of 8 channels, then you would use a frequency from the higher group.
an I to understand you only want a modem to use one or two frequencies instead of all 8?
in your config of the C4, you will see cable fiber-node. that is the number of channels/frequencies your setup to bond downstream and upstream. what tells the modems what's available for them to bond with

o.. i understand.
i set frequency from the 1st fiber-node, than the CM use this fiber-node. I set frequency from the 2st fiber-node, then the CM use this bonding. But what is, when the CM should use both bonding-(fiber)-groups?
can i set firm the usable frequencys from the bonding-group? Thats, what i will make. only the setted frequencys in CM config file should be used.

If I wanted to limit particular modems to a subset of the available downstream channels, I would create a bonding group for each such subset. Then I would add an attribute mask on these bonding groups. Then I would edit the CM config files and use CMDownstreamRequiredAttributeMask to force the CM to use that group.
More info here https://docsis.org/node/2337

o.k. currently i use dynamic bonding groups.
Now is will set cable fiber node with DS 13/0 13/1 13/2 13/3 13/4 13/5 13/6 13/7
and set bonding groups with attr mask 0x00000000 to manual Bonding group 1 (13/0-3) and attr mask 0x00000011 to manual to bonding group 2 (13/4-7)
then i will set the Attr Mask in CM Config File.
Questions:
- can i set 13/4-7 as no primary capable? (manual setted CM's should use both bonding groups (all channels 13/0-7)
- can i set all DS in one Fiber-node?
-on my C4 there is currently in DS Channel Config attr-mask 0x00000000, is this 0x80000000? What's the difference?
- must i set the attr-mask also on each DS Channel or only in Bonding-group?